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John J. Stachowicz
Assistant Professor of Evolution and Ecology
4345 Storer
(530) 752-1113
jjstachowicz[a]ucdavis.edu
CV: pdf
Ph.D., Marine Sciences, University of North Carolina at Chapel Hill (1998) |
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In the broadest sense, the unifying theme of my research is the ecological causes and consequences
of biodiversity. The vast diversity of life forms in the marine environment (many of the animal
phyla are exclusively marine, or nearly so) makes it a rewarding system for addressing these sorts
of issues. I have found seaweeds and marine invertebrates to be particularly tractable experimental
subjects and have conducted research involving a diverse suite of invertebrate taxa including
corals, hydroids, crabs, echinoderms, polychaetes, ascidians, bryozoans, and gastropods. The main
issues my research has focused on are:
(1) the importance of mutualism and commensalism in structuring communities
(2) the direct and indirect roles of biologically produced chemicals (secondary metabolites) in promoting biodiversity
(3) the functional importance of biodiversity in marine systems
(4) the causes and consequences of marine biological invasions
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Mutualism, facilitation and the structure of marine communities
Ecological investigations of the past several decades have focused on negative interactions
(competition and predation) and how they affect population and community structure. Although
positive interactions were studied decades ago, there has been limited effort to factor them into
our models or thinking about factors impacting populations and communities. My work tries to balance
this by using experimental investigations of positive interactions to study the population biology
of the participants and the effects of these interactions on communities as a whole.
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My empirical work has concentrated on the study of mutualisms and defensive associations in
which organisms that are susceptible to predators or overgrowth by competitors persist by living in association with another organism that locally ameliorates these conditions. I have found that in the absence of small sedentary herbivores that find shelter within their branches, many calcified plants and animals would be overgrown by superior competitors like fleshy seaweeds or fleshy invertebrates. Because corals and calcified seaweeds provide the biogenic structural complexity (i.e., reefs) on which many other species depend, these mutualisms are critical to the persistence of many marine communities. Thus, mutualisms are not simply natural history curiosities that make interesting stories, they also play an important role in organizing marine communities, allowing the persistence of key species in potentially unfavorable environments.
Recent publications:
Bruno, J.F., J.J. Stachowicz and M.D. Bertness. 2003. Incorporating facilitation into ecological theory. Trends in Ecology and Evolution (in press).
Stachowicz, J.J. 2001. Mutualisms, positive interactions, and the structure of ecological communities. BioScience 51:235-246.
Stachowicz, J.J. and M.E. Hay. 1999. Mutualism and coral persistence in algal-dominated habitats: the role of herbivore resistance to algal chemical defense. Ecology 80: 2085-2101.
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Chemical ecology and geographic variation in species interactions
Chemical ecology focuses on the ecological roles of 'secondary' metabolites, chemicals with no
obvious function in the primary metabolic demands of the cell. The term 'secondary' metabolite has
turned out to be a misnomer, as the use of these compounds as defenses against predators, competitors
and pathogens and as cues for the location of food, mates, and habitat can be as critical as
'primary' metabolites for the survival of organisms. In this area, I am currently collaborating
with Niels Lindquist at UNC-Chapel Hill to examine biogeographic patterns in the prevalence of
chemical vs. morphological defenses against predators in marine hydroids. I have also spent
considerable time examining how mobile marine invertebrates can exploit these chemical defenses for
their own benefit. For example, some decorator crabs place chemically defended seaweeds on their
backs, attaching them via hooked setae on their carapace. This strategy works to reduce predation
because this seaweed is distasteful to omnivorous consumers that eat both seaweeds and small
invertebrates like crabs.
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This research is sending me in two different directions. On one hand, I have developed a keen
interest in examining the genetic consequences of geographic variation in behavior as a result of
latitudinal gradients in selection pressure. On the community side of things, I have become
interested in the role that biogenic chemicals play in promoting local biodiversity, merging my
interests in chemical ecology with positive interactions. Current projects with several of my
students (Amy Larson, Kristin Hultgren) touch on each of
these themes.
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Recent publications:
Stachowicz, J.J. and M.E. Hay. 2000. Geographic variation in camouflaging behavior by the decorator crab Libinia dubia. American Naturalist 156:59-71.
Stachowicz, J.J. and N. Lindquist. (2000) Hydroid defenses against predators: the importance of secondary metabolites vs. nematocysts. Oecologia 124:280-288.
Stachowicz, J.J. and M.E. Hay. 1999. Reducing predation through chemically-mediated camouflage: indirect effects of plant defenses on herbivores. Ecology 80:495-509.
Stachowicz, J.J. 2001. Chemical Ecology of Mobile Marine Invertebrates: predators and prey, allies and competitors. Pages 153-190 in B. Baker and K McClintock, editors, Marine Chemical Ecology, CRC Press.
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The functional consequences of marine biodiversity
Given the rate at which biodiversity is being reduced by human activities, it is imperative
that we understand the relationships between species diversity and the structure, functioning and
stability of our ecosystems. Recently, I have been examining the relationship between species
diversity and the susceptibility of communities to invasion by non-indigenous species. The
introduction of exotic species into coastal marine systems has become an increasingly vexing problem.
These introductions may threaten the biodiversity of native species in these habitats, negatively
affect coastal resources, and have the potential to cause significant economic impacts.
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In experimentally assembled communities of sessile marine invertebrates, we found that reduced
native diversity enhanced the survival and percent cover of non-native invaders. Increasing
native diversity decreased the availability of open space, the limiting resource in this system,
by buffering against fluctuations in the cover of individual species. This occurred because
temporal patterns of abundance differed among species, so space was most consistently and
completely occupied over time when more species were present. This suggests that diversity of
functionally similar species may still have a positive effect on ecosystem processes when the
species occupy different temporal niches. The results from our small-scale experiments are
mirrored in large-scale field patterns, so we are confident that high diversity is important for
maintaining resistance to invaders, at least in this system. Thus, declining biodiversity may
result in an acceleration of the invasion process and homogenization of the global biota. The
link between marine biodiversity and other ecosystem functions (productivity, stability,
resistance to disturbance) is a very active area of investigation in my lab, including
collaborations with several of my graduate students (Randall Hughes,
Jarrett Byrnes).
Recent publications:
Stachowicz, J.J., H. Fried, R.B. Whitlatch and R.W. Osman. 2002. Biodiversity, invasion resistance and marine ecosystem function: reconciling pattern and process. Ecology 83:2575-2590.
Stachowicz, J.J., R.B. Whitlatch, and R.W. Osman. 1999. Species diversity and invasion resistance in a marine ecosystem. Science 286:1577-1579.
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Climate change and biological invasions
In addition to my work on the relationship between diversity and invasion success, I have been
examining the potential interaction between climate change and biological invasions. One obvious
prerequisite for a successful invasion is a match between the climatic tolerances of the invader
with the climate of the donor region. In areas with particularly harsh climates, climate may serve
as a barrier to the successful establishment of invaders, regardless of the rate of propagule supply
by ballast water, etc. However, climatic warming could lower these thermal barriers, particularly
in areas with very cold winters. Recently we analyzed a long term data set on the recruitment of
native and non-native marine invertebrates, and found that increased water temperatures in coastal
New England are likely to have facilitated the invasion of a number of exotic species in the past
three decades, including one in the last 3-4 years. This is because warmer winter temperatures allow
earlier seasonal onset of the recruitment of non-native species and ultimately increase the overall
magnitude of invader recruitment. Warmer winters have the opposite effects on natives. Our data
suggest that the greatest effects of climate change on biotic communities may be due to changing
maximum and minimum temperatures rather than annual means. This suggests that ecological effects of
climate change may be difficult to predict because effects may be concentrated during the portions
of the year when temperatures are most extreme or when species pass through critical life-history
stages.
Recent publications:
Stachowicz, J.J., J. R. Terwin, R. B. Whitlatch and R.W. Osman. 2002. Linking climate change and biological invasions: ocean warming facilitates non-indigenous species invasion. Proceedings of the National Academy of Sciences USA 99:15497-15500.
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